Plastic containers have been used as a replacement for glass or metal containers in the packaging of beverages for several decades. The most common plastic used in making beverage containers today is polyethylene terephthalate (PET). Containers made of PET are transparent, thin-walled, and resistant to deformation by forces exerted on walls of the container by opposing forces of contents packaged in the containers. PET resins are also reasonably priced and easy to process. PET bottles are generally made by a process that includes blow-molding of plastic pre-forms made by injection molding of the PET resin.
Knowledge of material thickness is beneficial in a production of containers, such as PET bottles, for a multitude of reasons, typically including process and quality control. As will be recognized, knowing the thickness of the material of the containers is critical for limiting unneeded material being included in the containers, thereby conserving material resources and limiting production expenditures.
Some conventional solutions for measuring container wall thickness are capable of measuring with an accuracy of 1 micron (μm), but these solutions lose their accuracy at speeds typically involved in the manufacturing of the containers. Although some conventional systems are capable of higher speed measurements, the accuracy of such high-speed systems generally is about 20 μm, and the systems are capable of capturing relatively fewer data points from each container than is desired. Further, conventional high-speed systems generally can only measure a relatively small number of discrete points or regions on a container.
What is needed, therefore, are high-speed measurement systems and methods capable of accurately determining container wall thicknesses, potentially of an entirety of each container, while the containers move at speeds encountered during the manufacturing process.